Who is Bran de Montfort from The Reckoning and what is their importance?

Bran de Montfort is Simon's son. He is supposed to bring soldiers to Simon's aid in Evesham, but he arrives too late. Haunted by the images of his slain brother and father, Bran questions his loyalties and suffers great guilt over the death of his family members. His brother Guy seeks revenge against their cousin Hal in Italy, and Bran blindly follows his lead, knowing that it's wrong. When Guy murders Hal and a priest in front of an entire congregation, both brothers are excommunicated by the church.